Roadster Owner Based Study of Battery Pack Capacity Over Time

[davidrmay]

10 days of no charging

Slightly off theme but battery related... If I leave car for 4-5 days and it does not get driven should I change it to storage mode to prevent standard mode from recycling at 95% to 97% each night ..... holding this charge constant for that period of time?

I was just on vacation and could not keep car plugged in. I was told it would be fine by Tesla.
It was 10 days between charges. I noticed no change when I started charging again (and could not detect change in battery level either).

I've been pulling my logs.

- David

 

[Botbldr45]

Thanks for suggestions....... Just changed mode via Tattler from 1000 miles away. ....... So cool!

 

[dsm363]

Bump to remind everyone to gather log files from their cars, get the updated log parser and send results.
Especially interesting is anyone with over 30,000 miles or has a car that had an out of balance battery.

Do you want just the most recent one or all the ones we've collected? I'm sure I have gaps in time since I don't remember to pull the logs each month.

 

[Botbldr45]

Pulling logs sounds like a good thing to do. If the information can help us understand our batteries better I'm all for it.
Problem: I'm not the most computer literate individual so I'm sure your going to hear some really stupid questions in future blogs.
Sorry!

 

[dsm363]

There are more options on the PC but you basically stick the USB thumb drive that came with your car into the USB port below the VDS maybe once a month. It takes about 15 minutes or so while the car is parked to download the data. A screen pops up on the VDS telling you not to remove the USB drive. The rest of the details are in another thread on the forum about what the various programs are.

 

[richkae]

Do you want just the most recent one or all the ones we've collected? I'm sure I have gaps in time since I don't remember to pull the logs each month.

If you want to send the raw log files then please send them all ( unless you remember which ones you have sent in the past and only send the new ones ).
If you just want to send the output from the log parser, then you run it from a directory that contains all the log files you have ever downloaded from the car and run "vmsparser -b *.tar >output.txt". When you do that, the parser uses all the available data and skips over the gaps.

If you send the raw files, then when improvements are made to the parser, I can re-run the files without asking you to resend the data. I included the option of just sending the output of the parser because there may be data in the log files that people do not want to share. Supposedly there is encrypted GPS data in the log files, but I do not know how to read it, nor how to decrypt it, nor do I have the decryption key. But with encryption it is always possible that it has flaws that make it easy to crack. The files are stored on my home computer and backed up on my NAS ( unencrypted ). If someone stole my computers then they would have whatever you sent.

When you run the parser with -b it outputs the following data sections ( this is from memory, as I don't have it in front of me - but it is a text file you can inspect ):
1) time spent at SOC%
2) time spent at temp
3) time spent charging at each amp level
4) a summary of distance traveled over time ( I think it is how long did each 1000 miles take to accumulate )
5) battery amp-hour stats per day
6) firmware revision history

Lastly, please send a quick note detailing any battery replacement you have had done. If you have had any sheets, or the entire battery replaced - please try to include the date that happened to the best of your recollection. If you are the second owner of the car, and do not know what happened to the battery before you owned it, it would be very good to know the date you aquired the car.

 

[tomsax]

Supposedly there is encrypted GPS data in the log files, but I do not know how to read it, nor how to decrypt it, nor do I have the decryption key.

To be clear, the only known GPS data in the log files is just a table of the places you've charged. As far as I know, no one has made any progress breaking the encryption and we're pretty convinced there isn't any other GPS data in the log files.

 

[lmore]

Using the OVMS to compare two Roadsters over several days, I noticed that for one of the cars, the battery pack temperature is 8-15 °C higher than the ambient temperature.

While for the other car the battery pack temperature is roughly equal to the ambient temperature. The ambient temperature has been in the range 15-20 °C. The comparison is done when the car have been parked and not driven.

Can this be an indication that the "warm" battery pack has a problem?

 

[JRP3]

If they are parked in the same place I'd say that something unusual may be going on to cause that much temperature difference. Vehicle color may have some effect but I wouldn't think that much.

 

[tomsax]

Using the OVMS to compare two Roadsters over several days, I noticed that for one of the cars, the battery pack temperature is 8-15 °C higher than the ambient temperature.

While for the other car the battery pack temperature is roughly equal to the ambient temperature. The ambient temperature has been in the range 15-20 °C. The comparison is done when the car have been parked and not driven.

Can this be an indication that the "warm" battery pack has a problem?

It would be interesting to see logs from each car. PM me if you'd like me to take a look.

 

[markwj]

Using the OVMS to compare two Roadsters over several days, I noticed that for one of the cars, the battery pack temperature is 8-15 °C higher than the ambient temperature.

Are you sure the temperature subsystem in the car is not "asleep" and not updating?

To be sure, I would suggest that the next time you drive, call up the temp display on the VDS. Also, in the iPhone App tap on the boot of the car and then choose Wakeup to get updated readings.

 

[lmore]

This is something I have seen over several days, under different conditions. Now, for example, the "warm battery" car has an ambient temp of 10 C while the battery temp is 21 C (car is plugged in and probably done charging several hours ago at 12 amp/220 Volts). I will pull the log files files when I get to access the cars, appreciate the help!

 

[dhrivnak]

Has the program name changed? I downloaded and installed the Tesla log parser called TeslaGLOP.exe. It does not allow me to pipe files to it. I now have over 10,000 miles and was going to submit my logs again. I have been tracking my range in STD mode for nearly a year now and I have not seen any drop in capacity. Thank you

 

[tomsax]

Has the program name changed? I downloaded and installed the Tesla log parser called TeslaGLOP.exe. It does not allow me to pipe files to it. I now have over 10,000 miles and was going to submit my logs again. I have been tracking my range in STD mode for nearly a year now and I have not seen any drop in capacity. Thank you

That's a different log parser. For this study, you need to use my command line app.

Complete instructions are here: VMS Log Parser for Tesla Roadster. Download the program then follow the instructions in the "Battery Longevity Study" section. The section "Using a Command Line App" may be helpful for those who haven't used one before.

 

[Ben W]

Chiming in with a random data point: my 3 1/2 year old Roadster with 31k miles on it just completed a full charge in Range mode, and shows 222 ideal miles. This represents a loss of roughly 3% capacity per year. I can live with that, though I'm still hoping for a 400-mile replacement pack upgrade when it comes time in 2016 ;-)

 

[richkae]

Here is a summary of all the data I have.
Some of the data is very old ( 6 months ), a couple of the submissions were made by a very old version of the log parser that had some bugs, and I could not get useful data of it.

Here is a chart of battery capacity vs miles driven:

You'll notice one data point that stands out as having a low capacity after only 11000 miles. That car sat for a very long time unused, and the data was submitted after it changed owners after that long period of disuse.
I believe that the battery needs to be cycled a few times to discover its true capacity, as the computer is being conservative.

Here is a chart of battery capacity vs age in years:

I believe that this is evidence that there is not a lot of capacity loss due to age, it is primarily a function of miles driven. The data point that stands out in this chart is actually a car that has driven 51k+ miles in 1.5 years.
There are fewer data points in this chart because some of the data is truncated - the oldest data is lost - and I don't know how old the car actually is.

 

[dhrivnak]

Can yo translate capacity to ideal miles or kwh? As i never had it new i am not sure where i am on the chart. Thank you.

 

[richkae]

Ideal miles in range mode should be = percentage from chart * 245
I used the amp hours from the average brick to compute the percentage, that may be wrong - it might be necessary to use the minimum brick.
The minimum brick is usually within 1% or 2% of the average brick. So that would skew all the numbers down a little, unless the car has one very low brick.

 

[richkae]

This chart includes the average brick and the minimum brick. Clearly understanding how ideal miles relates to the average brick and the minimum brick is important.

 

[SCW-Greg]

Hey not that I own a Tesla yet, but working on it... I just want to give a shout-out to Richkae (as well I'm sure of the parallel internal efforts of Tesla), for doing this pioneering research. It will aid Tesla, and it will aid us all in future vehicles/battery packs to be totally brainless/transparent charging efforts. The entire community benefits from those who are sharing their logs, and Richkae's ongoing volunteer work.

thx!